During surgery, or as a result of trauma, subcutaneous tissue can be removed or altered, and an open void or dead space or cavity is created within the tissue that was previously attached to other tissue. This may also occur inside the chest or abdominal cavity. The very small blood and lymphatic vessels that previously ran from the underlying tissue (i.e., muscle, connective tissue) to the overlying tissue (i.e., skin, muscle) can be cut or damaged. When this occurs, the natural process of wound healing is triggered.
The process of wound healing is well known. When an initial incision is made at the beginning of a surgical procedure, or following a traumatic wound, the body conveys blood, blood products, and proteins into the cavity or void or operative dead space that is formed. A wound exudate begins to form. This initiates the first stages of wound healing.
The production of wound exudate occurs as a result of vasodilation during the early inflammatory stage of wound healing. It occurs under the influence of inflammatory mediators, such as histamine and bradykinin. Wound exudate presents itself as serous fluid in the wound bed.
Wound exudate is part of normal wound healing in acute wounds. Wound exudate contains proteins and cells that are vital to both initiate and propagate the healing process. The constituents of wound exudate include, inter alia, (i) fibrin (function: clotting); (ii) platelets (function: clotting); (iii) other cellular elements, e.g., red blood cells and white blood cells including, lymphocytes, neutrophils and macrophages; and (iv) wound debris/dead cells.
The blood cells, blood products, and proteins within the wound void or cavity initiate the coagulation cascade. The blood inside the void or operative dead space mixes with the proteins and begins to form clot. Fibrin forms from fibrinogen, and the process of clotting and wound healing is initiated. The coagulation cascade begins immediately after incision or injury, and typically continues until about the fifth to seventh day of wound healing. The end result of the coagulation cascade is the formation of thrombus and clot. It is this natural clotting process that avoids exsanguination, else the person would bleed to death.
Thus, as part of the normal wound healing process, it is to be expected that fluid collecting in the wound void will include wound exudate, blood cells, blood products, blood clots, thrombus, wound debris, dead cells, and other byproducts of wound healing. The larger the operative dead space, the greater is the potential for internal fluid collection.
Due to the progression of the wound healing process, it is well known that the constituency of the fluid within the operative space changes over time. In the early stages of wound healing, as the byproducts of wound healing form, the fluid is bloody and viscous. Only after wound healing progresses, and the coagulation cascade advances to repair the injury, does the fluid in the wound void turn less bloody and viscous, into a straw-colored serum. Anyone having surgery where a drain is placed has experienced the fluid changing from a thick bloody drainage to a more clear yellow or serous color.
A person who is in good health, or has minimal skin undermining or has otherwise undergone a minor procedure, can resolve the accumulation of fluid within a wound void over time. However, the body still has fluid that collects in the open space. This open space needs to fill with the exudates, which facilitates closure of the dead space, approximation of the tissues, and normal healing. Wound healing also needs to be accompanied by an absence of continued irritation, so that there is not a continuous initiation of new wound healing.
Currently, to aid the evacuation of fluid from the wound, conventional wound drains are placed at the end of a surgical procedure.
There is a recognized problem with conventional wound drain technology, which is directly related to the nature of the wound healing process itself. Effective wound drainage necessarily requires the ability to clear the byproducts of the wound healing process, as described, such as wound exudate, blood cells, blood products, blood clots, thrombus, wound debris, dead cells and other viscous materials. However, experience demonstrates that these naturally occurring byproducts of wound healing plug conventional wound drains. As a result, current wound drain technology is not effective at adequately clearing wound voids. Concurrently, current drains are ineffective at formally closing down larger dead spaces, and can only manage small amounts of fluid directly around the drain itself. Fluid can quickly overwhelm the space and collect to large volumes, creating a seroma and preventing the tissue surfaces from approximating and healing. Finally, conventional wound drains provide non-uniform blood and fluid removal with low inconsistent suction pressure, often with long drain duration and the potential of infection. The wound void is not closed down, and seroma formation remains high and persistent.
As a result, seromas commonly develop following drain removal or when fluid is produced at a greater rate than can be absorbed. Conventional wound management techniques are commonly applied when a seroma becomes a clinical concern. Placement of a seroma catheter or additional drain, as well as repeated or serial drainage of a seroma, may be required, which involved recurrent, serial punctures often over two to three weeks, until the seroma cavity is closed or is no longer a clinical problem.
Another option is to place a “Seroma Cath”™. A clinically accepted way to deal with a seroma that does not appear to be resolving on its own, is to replace a new surgical that continuously drains the space system, coupled with treatment with antibiotics to prevent infection while the current drain system is in use. There are currently numerous types of wound drains on the market, most of them utilizing some form of tubing to withdraw fluid from the wound until the body can resorb the fluid without assistance. A continuous drain system allows the fluid to continuously escape until the body can complete the healing process on its own.
A representative prior art continuous drain system can comprise an implanted device such as a piece of rubber tubing (Blake Drain) (as shown in FIG. 1), which provides dependent gravity drainage or responds to a negative suction force generated by a manual closed suction bulb. These types of drains constitute the most common devices currently available. The problem with these devices is that they may become plugged by blood clots carried by the wound fluid, or may be overwhelmed by the fluid generated in the space, or may have such low continuous pressure that they are ineffective at closing the internal space down. So pervasive is the problem of plugging and seroma formation with conventional wound drains that the Home Care Instructions for using the drains include instructions for “stripping or milking” the drains when clots need to be cleared from the drains. Further, although they may, when not plugged, drain fluid, fluid drainage is limited to fluid directly around the drain itself. As a result, current drains again, at best, do not effectively clear all of the fluid in the space and, more importantly, they do not clear enough fluid to effectively seal down and close off the dead space. In essence, any fluid in the dead space effectively blocks the tissues from approximating or coming into contact with each other preventing or delaying the normal wound healing process.
Another representative prior art continuous drain system, which is currently approved for external use only, can take the form of an externally applied device comprising a piece of foam with an open-cell structure, which coupled to one end of a plastic tube (see FIG. 2). The foam is placed externally on top of the wound or skin, and the entire external area is then covered with a transparent adhesive membrane, which is firmly secured to the healthy skin around the wound margin. The opposite end of the plastic tube is connected to a vacuum source, and fluid may be drawn from the wound through the foam into a reservoir for subsequent disposal. This prior art system has been called a “Vacuum Assisted Closure Device” or a VAC device. Conventional VAC devices, however, are only approved and used for external wounds. Conventional VAC devices are not approved or used for internal wounds or operative sites, and may create bleeding upon withdraw and leave particulate matter from the foam inside the wound base.
Current wound drain devices assemblies at times do not remove a substantial amount of fluid from within a wound and have other performance issues. For example, external VAC devices clear fluid directly around external wounds (as FIG. 3 shows), and they are limited to the application to external wounds only. They leave the remainder of the wound site or operating space open, which must be allowed to heal in on its own by “secondary intention,” or closed surgically at another point in time.
Furthermore, the clinical use of external VAC devices may not make wound drainage more cost-effective, clinician-friendly, and patient-friendly.
For example, the foam structures and adhesive membranes associated with conventional practices of external VAC need to be periodically removed and replaced. Currently, dressing changes are recommended every 48 hours for adults with non-infected wounds, and daily for infants and adolescents. Current techniques place the foam material in direct contact with granulating tissue. Removal of the foam structures in the presence of granulating tissue and the force of pressure on the wound bed that this removal can cause pain or discomfort. The foam sponge can also de-particulate and remain in the wound. Furthermore, the multiple steps of the conventional external VAC procedure—removing the adhesive membrane, then removing the old foam structures, then inserting the new foam structures, and then reapplying the adhesive member along the entire periphery of the wound—are exacting, tedious and time consuming. They only prolong pain or discomfort, and cause further disruption to the patient, and also demand dedicated nursing time and resources.
Furthermore, to function correctly, the adhesive membrane applied over the foam wound structures must form an airtight seal with the skin. Obtaining such a seal can be difficult, particularly in body regions where the surrounding skin is tortuous, and/or mucosal and/or moist.
Furthermore, prolonged wearing of wet dressings can cause further breakdown and maceration of the surrounding skin thereby increasing the wound size. This can cause further discomfort to the patient, and the exudate can often be offensive in odor and color causing further morbidity to the patient. This may, in turn, require more numerous dressing changes and re-padding throughout the day, which is disruptive to the patient and costly both in terms of nursing time and resources.
Furthermore, since the membrane and the material of the foam structures are both in direct contact with tissue, tissue reactions can occur.
A seroma or fluid collection in closed interior wounds is by far the most common complication in surgery today. Such complications result in a significant amount of lost income to patients, as well as expenses to insurers and physicians who have to care for these patients that require serial drainage. Such complications also delay wound healing, may entail additional surgical procedures, and ultimately delay the patient's return to work and routine functional activity. Seroma management can also be costly and, further, can place health care workers to additional needle exposure risks and related outcomes such as hepatitis, etc. Concurrently, there are millions of dollars being spent on developing internal glues to try to get internal tissues, separated by surgery, to adhere back together following surgery.
The inability to prevent or treatment seromas that form in closed interior wounds is a problem that has persisted in the field of elective surgery since the beginning of surgery, and has been documented in the surgical literature for all specialties over the last fifty years. Seromas and abnormal fluid collection are so common, that physicians and surgeons will acknowledge that seromas are, unfortunately, an expected part of wound healing following surgery.
However, it does not have to be this way.